THERMODYNAMIC PROPERTIES OF SILICATE MELTS

Fraser D. G. (1977). Thermodynamic properties of silicate melts. In Thermodynamics in Geology. D. G. Fraser, ed. Reidel, Dortrecht-Holland. 

The thermodynamic properties of silicate melts however, are complicated by the presence of a large number of different silicate anions. While silicate minerals are usually monor disperse, containing only a single type of anion (e.g. SiojJ in olivine), molten silicates contain a distribution of different polymeric silicate anions of different molecular weights and are thus polydisperse systems. The presence of a distribution of silicate anions in the melt can be inferred from the mixing properties of silicate melts (Richardson, 1956 Masson, I965). However, it has recently become possible to separate some of the... 

In 1963 Dr. Danbk joined the Institute of Inorganic Chemistry of the Slovak Academy of Sciences in Bratislava, of which he was the director in the period 1991-1995. His main field of interest was the physical chemistry of molten salts systems in particular the study of the relations between the composition, properties, and structure of inorganic melts. He developed a method to measure the electrical conductivity of molten fluorides. He proposed the thermodynamic model of silicate melts and applied it to a number of two- and three-component silicate systems. He also developed the dissociation model of molten salts mixtures and applied it to different types of inorganic systems. More recently his work was in the field of chemical synthesis of double oxides from fused salts and the investigation of the physicochemical properties of molten systems of interest as electrolytes for the electrochemical deposition of metals from natural minerals, molybdenum, the synthesis of transition metal borides, and for aluminium production. 

Two specific examples of the application of thermodynamic methods to geological problems are considered by Wones and Dodge (biotites as monitors of granitic melts) and by El Goresy and Woermann (opaque minerals as oxygen barometers and geothermometers). These are followed by a section on the thermodynamic properties of melts. Following a review of the properties of "simple" molten salts (Kleppa) the nature and properties of silicate melts are considered by Fraser. This is followed by a chapter by Nicholls on the treatment of activities in natural silicate melts and a discussion of trace element behaviour by O Nions and Powell. 

Mysen B. O., Virgo D., and Scarfe C. M. (1980). Relation between the anionic structure and viscosity of silicate melts A Raman spectroscopic study. Amer. Mineral, 65 690-710. Nafziger R. H. and Muan A. (1967). Equilibrium phase compositions and thermodynamic properties of olivines and pyroxenes in the system MgO-FeO-SiOj. Amer. Mineral, 52 1364-1384. 

For Earth scientists, concerned primarily with the properties of minerals, silicate melts, aqueous solutions and gases at elevated temperatures and pressures, sources of data for thermodynamic calculations presents an unending challenge. This challenge is at two levels—first, do the necessary data exist, and second, if there are several sets of data, which one to choose, i.e., which is the best ... 

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